Earlier this year my Patrol started feeling decidedly sluggish, one could feel that there was no power. After a long search for the culprit (and the very necessary replacement of the turbo), I eventually took it to Koos Swanepoel Developments in Stikland where they put it on the Dyno and within half an hour they told me that the MAF sensor was faulty.

The sensor is supposed to vary between 0 and 5V depending on the airflow and mine was stuck on 1V.

I replaced the MAF sensor with a Nissan part (~R2k VAT incl) and took it back to them to ensure that the boost hasn't been turned up too high etc.